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Carbon Nanomaterials for Zn-Ion Batteries

Prasun Banerjee1*, Adolfo Franco Jr2, Rajender Boddula3, K. Chandra Babu Naidu1 and Ramyakrishna Pothu4

1Department of Physics, Gandhi Institute of Technology and Management (GITAM) University, Bangalore, India

2Institute of Physics, Federal University of Goiás, Goiânia, Brazil

3CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, China

4College of Chemistry and Chemical Engineering, Hunan University, Changsha, China

Abstract
The development of the zinc-ion battery (ZB) hindered due to the problem associated with the suitability of its design especially on the catalyst and electrodes parts. Modified surface of carbon can enhance oxygen reduction reaction significantly for the catalytic performances. An ultimate design of ZBs should contain proper synthesis along with a precursor-like nitrogen with carbon-metal support for enhanced performances of ZBs. Electrodes formed with N-doped carbon fiber network with Co4N NPs not only provide high current density but also flexibility to ZBs. The ORR of ZBs can also be increased by using the N-doped carbon nanofiber (NCN). The enhancement of OER/ORR activity has been observed by coupling NiCo2S4 nanocrystals with nitrogen-doped carbon nanotubes (N-CNT/ NiCo2S4) for electrocatalyst applications in ZBs. P and S co-doped C3N4 sponge with C nanocrystal (P-S-CNS) demonstrated good OER and ORR activity. The OER and ORR performance can also be enhanced with the use of carbon nanosheets because of its greater surface area. The morphology and the porous structure in the N-rGO/NC cathode surface OER and ORR activity in ZBs.

Keywords: Zinc-ion battery, carbon, nanocomposites, oxygen-reduction, oxygen-evolution

1.1 Introduction

The demand of storage energy especially without depending much on fossil fuels has been accelerated recent years with the progress in the battery field technologies [1-7]. The use of lithium undoubtedly makes it the leader in this sector. But, for the sake of electric vehicles (EVs), the use of lithium increase the cost many folds which is one of the reasons of unpopularity of EVs in the consumer vehicle market [8, 9]. In these sense, zinc, the 4th abundant metal in the world, can help to increase the popularity of the EVs by diminishing the cost the vehicles [10]. Theoretically, the zinc battery (ZB) possesses five times the energy density with respect to the lithium batteries. Hence, they are much more superior to that of its lithium counterpart both theoretically as well as economically. Despite of all this the advantages of ZB technology, its development highly hindered due to the problem associated with the suitability of its design especially on the catalyst and electrodes parts [11]. Modified surface of carbon can enhance oxygen reduction reaction significantly for the catalytic performances [12]. Hence, an ultimate design should contain proper synthesis along with a precursor-like nitrogen with carbon-metal support for enhanced performances of ZBs.

1.2 Co4N (CN) - Carbon Fibers Network (CFN) -Carbon Cloth (CC)

Electrodes formed with N-doped carbon fiber network with Co4N NPs shown in Figure 1.1 [13]. Meng et al. observed enhanced catalytic performances of CN/CFN/CC as an electrode in ZBs [13]. The following design not only provides 1 mA cm-2 current density but also flexible nature to ZBs in contrast to the conventional metal electrodes. The design can withstand 408 cycles with 1.09-V discharge-charge gap at 50 mA per cm2 with 20 h of retention of current density. Moreover, the flexible nature of the ZBs makes it a perfect power source for a wide range of wearable portable devices.

1.3 N-Doping of Carbon Nanofibers

The ORR of ZBs can enhance with the N-doped carbon nanofiber (NCN) as shown in Figure 1.2 [14]. Here, large surface area as well as the exposure of the NCNs increased the ORR activity. The use of NCNs can surpass the peak power density of available platinum/carbon catalyst of magnitude 192 mW cm-2 to by using NCNs in ZBs with a new magnitude of 194 mW cm-2 [14]. Moreover, the superiority of NCNs can also helps to achieve better electron numbers and hydrogen peroxide yields than that of the platinum/carbon catalyst.

Figure 1.1 (a) Steps of Synthesis, (b)-(d) SEM images, (e) XRD, (f) TEM images and (g) EDS of CN/CFN/CC electrodes. Reprint with the permission from Reference [13]. Copyright 2016, ACS.

Figure 1.2 (a) ZB, (b) division of air electrode, (c) polarization graph, and (d) power density graph. Reprint with the permission from Reference [14]. Copyright 2013, Elsevier.

1.4 NiCo2S4 on Nitrogen-Doped Carbon Nanotubes

The enhancement of OER/ORR activity has been observed by Han et al. by coupling NiCo2S4 nanocrystals with nitrogen-doped carbon nanotubes (N-CNT/NiCo2S4) for electrocatalyst applications in ZBs [15]. The reversibility, stability, and bifunctional activity as shown in Figure 1.3 were up to the level of well-known metal catalysts performances. More positive cathode potential has been observed for N-CNT/NiCo2S4 in compression to its counterpart. Hence, this new design with carbon composites along with chalcogenides enables better performances for the ZBs.

Figure 1.3 (a) Cyclic and (b) Linear voltammograms, (c) peroxide (solid) and no. of electrons (dotted), (d) K-L graph, (e) Tafel graph, (f) current densities of NiCo2S4, CNT/NiCo2S4, and N-CNT/NiCo2S4. Reprint with the permission from Reference [15]. Copyright 2017, Elsevier.

1.5 3D Phosphorous and Sulfur Co-Doped C3N4 Sponge With C Nanocrystal

P and S co-doped C3N4 sponge with C nanocrystal (P-S-CNS) demonstrated good OER at 10 mA per cm2 current density with 1.56 V. The ORR activity also enhanced up to 7 mA cm-2 with 1-V potential [16]. Figure 1.4 also showed that the power density with the use of P-S-CNS in ZBs can reach up to 200 mW per cm2 at 200 mA per cm2 current density. Not only that, it can provide emf of 1.5 V at a specific capacitance of around 830 mAh per g1. The energy density also can reach up to 970 Wh per kg1 at 5 mA per cm2 current density. The reversibility and stability also enhances up to 500 cycles. Hence, the use of P-S-CNS in place of precious metals indeed demonstrates a cleaner and greener way of storage devices with respect to the conventional batteries.

Figure 1.4 (a) ZBs; (b) Power density; (c) Galvanostatic discharge graphs; (d) Specific capacity; (e) Stability; (f) Simple demonstration with P-S-CNS. Reprint with the permission from Reference [16]. Copyright 2016, ACS.

Figure 1.5 SEM images of 2D carbon nanosheets. Reprint with the permission from Reference [17]. Copyright 2015, RSC.

1.6 2D Carbon Nanosheets

The larger surface area of 1,050 m2 per g of the nanosheets of carbon indeed makes it suitable for the application of the ZBs [17]. Figure 1.5 shows the SEM images of the 2D structure of the nanosheets. The OER and ORR performance can be enhanced with the use of carbon nanosheets because of its greater surface area which increase the oxygen absorption and enhance the catalytic activities in many folds. The platinum/carbon galvanic discharge voltage 1.2 V of current density of 5 mA per cm2 can be achievable using the carbon nanosheets in ZBs. Hence, the competitive performances with the low cost of production indeed make it a suitable choice to use in the ZBs.

1.7 N-Doped Graphene Oxide With NiCo2O4

Graphene oxide with N-doped along with NiCo2O4 (N-rGO/NC) can be used as another stable cathode electrode for the ZBs applications [18]. The flower-like structure of the N-rGO/NC is shown in Figure 1.6. The flower-like structure helps to obtain 4-V plateau in the charge profile whereas the plateau is situated around 2.6 V for the discharge profile. The capacity of the ZBs with the use of N-rGO/NC cathode can reach up to 7,000 mAh g-1 till 35 h. The morphology and the porous structure in the N-rGO/NC cathode surface help better flow of oxygen which enhances the OER and ORR activity.

Figure 1.6 SEM, TEM, and XRD N-rGO/NC. Reprint with the permission from Reference [18]. Copyright 2017, RSC.

1.8 Conclusions

In summary, the development of the zinc-ion battery (ZB) hindered due to the problem associated with the suitability of its design especially on the catalyst and electrodes parts. Modified surface of carbon can enhance oxygen reduction reaction significantly for the catalytic performances. An ultimate design of ZBs should contain proper synthesis along with a precursor-like nitrogen with carbon-metal support for enhanced performances of ZBs. For example, electrodes formed with N-doped carbon fiber network with Co4N NPs not only provide 1 mA cm-2 current density but also flexibility to ZBs. The ORR of ZBs can also increase with N-doped carbon nanofiber (NCN). The enhancement of OER/ORR activity has been observed by coupling NiCo2S4 nanocrystals with nitrogen-doped carbon nanotubes (N-CNT/NiCo2S4) for electrocatalyst applications in ZBs. P and S co-doped C3N4 sponge with C nanocrystal (P-S-CNS) demonstrated good OER 10 mA per cm2 current density with 1.56 V. The ORR...